The present invention relates to container forming apparatus, and more particularly to a machine for drawing and ironing one-piece metal container bodies.
The prior art is replete with examples of various types of mechanisms adapted to draw, iron, or to draw and iron, metallic blanks so as to form cup-like one piece metal container bodies. Such apparatus commonly comprise an elongate, cylindrical ram which is adapted to urge cupped metal blanks through a series of annular dies of progressively smaller diameter. This procedure accomplishes two ends: it progressively thins the lateral walls of the cylindrical container being formed over the end of the ram, and causes the metal so displaced to cold flow along the surface of the ram so as to axially elongate the side walls of the container. The container may then be stripped from the end of the ram; or, if a particular configuration such as the widely-used concave indentation is to be imparted to the container bottom a resilient "doming" die is provided to receive the ram at the furthest point of its advance, and the end of the ram is provided with a suitable mating configuration. The cooperation between the end of the ram and the doming die indents or domes the container bottom, after which the ram may be withdrawn from within the container body and the body transferred by means of a outfeed mechanism to subsequent machinery for trimming, capping, etc.
The elongate ram described above is commonly carried by a reciprocative element termed a carriage. The carriage is supported by and rides in guides or ways formed in the main frame of the machine proper. The carriage is commonly provided with rollers, or arranged to slide upon a lubricated surface in the manner of a hydrostatic bearing. In order to effect reciprocation of the carriage it is known to use either hydraulic means, or a mechanical linkage such as a crankshaft and connecting rod arrangement. With most prior art devices, a problem arises when it is desired to adapt a container-forming mechanism to produce containers of varying depth. In order to accommodate the deepest container to be formed, a relatively long stroke must be provided to the carriage. However, when forming relatively shallow containers much of the travel of a long stroke is superfluous and comprises wasted time and effort.
A further problem which inhered in many prior art arrangments was the difficulty in minimizing the "runout", or lateral deviation from an ideal path, of the carriage and thus of the ram which it carries. Due to the necessarily small clearance between the ram and the annular ironing dies through which it passes, slight deviations from concentricity result in the formation of containers with unacceptably thin wall sections. As the elongate ram extends a considerable distance from the forward end of the supporting carriage, it will be appreciated that small deviations or runout in carriage travel are in effect amplified by the relative length of the ram and so may cause major lateral deviations at the ram end. While a portion of the runout of the carriage can be eliminated by careful adjustment of machine bearings and ways, a certain amount of clearance is always necessary. This clearance inherently produces a degree of lateral movement of the carriage when it is subjected to substantial lateral forces by the driving mechanism.
While the carriage is conventionally urged forward and back by pivoted linkages which may include low-friction bearings or bushings, as exemplified by U.S Pat. No. 3,270,544 -- Maeder et al, a certain amount of lateral force is nonetheless transmitted from the driving linkage to the end of the carriage. Since the linkage is often coupled to the rearmost portion of the carriage, the leverage thus provided may result in an unacceptable cocking or lateral deviation of the carriage.
Also as depicted in the aforementioned U.S. Pat. No. 3,270,544 it is known to provide an elongate extensible stripper punch within an ironing ram for aiding in the removal of a finished container from the ram end. Such a stripper punch is commonly in the form of an elongate rod or tube, and is periodically urged forward by mechanical means. When such mechanical means are mounted upon the carriage which supports the ram, additional forces are brought to bear upon the carriage which further deflect it from its desired path along the ways of the machine frame.
The mechanism used to operate the stripper punch has long presented a difficult design problem due to the fact that the punch is carried within the reciprocating carriage. In one prior art approach, shown in U.S. Pat. No. 3,712,107, a stationary cam is disposed near the ways in which the carriage rides, and an element coupled to the stripper punch extends from the carriage for engaging the stationary can. This approach, however, has serious deficiencies including the accelerated wear which may occur if the system is adapted to control the operation of the punch throughout its entire travel. U.S. Pat. No. 3,702,559 -- Hasselbeck et al also suggests the use of a cam, but of the cumbersome and expensive drum variety.
In other cases the stripper punch has been spring biased, and periodically urged from within the ram when an extended portion of the punch encounters a stationary member located adjacent the path of the carriage. In this case, however, the return of the stripper punch to a seated position within the ram is occasioned by the sudden release or disengagement of the stripper punch by the stationary element, so that the punch undergoes a severe impact as it is seated within the ram by the force of the biasing spring.
It has been conventional to drive each container forming machine with individual motive means, such as a large electric motor. Such a motor is commonly coupled by means of a belt drive to a large flywheel for maintaining consistent operation of the machine, as is well understood by those skilled in the art. Coupled to the flywheel in turn is a suitable clutch assembly, along with means carrying a crankpin offset from the center of rotation for imparting reciprocal motion to the carriage within the machine. This arrangement, while relatively straightforward, necessitates the provision of a bulky and expensive driving mechanism for each machine and moreover prevents the close positioning of multiple machines in a factory. Consequently, a plurality of machines require an inordinately large floor space.
In some cases it is desirable to perform an additional drawing operation on metal blanks preparatory to the elongation or ironing of the blanks. To this end, it is known to position an annular drawing die concentrically with the machine ram, and advance it along with the ram for the initial portion of the ram's travel. During the first stage of this operation the ram remains disposed within the confines of the surrounding drawing die, so that the ram and drawing die advance together as a single unit to force a metal blank into a cooperating female drawing die. The ram then advances through the abutted drawing dies, pulling the metallic blank therethrough and subsequently through the succeeding ironing dies. In order to properly locate the drawing die and operate it in synchronism with the ram, various mechanical drive systems have been devised. However, in order to provide the proper synchronism and motion to the drawing die it is commonly been necessary to add an entire motive mechanism to the container forming machine, which adds considerably to the cost and complexity of the machine.
It will therefore be seen that it would be desirable to provide an improved container forming machine, including a compact auxiliary drive mechanism for a drawing die attachment. It will also be understood that it would be highly desirable to provide a one-piece container forming machine which has an improved stripper punch mechanism, and having a ram-carrying carriage less susceptible to lateral displacement than any heretofore known in the prior art. Finally, it will be evident that it would be advantageous to provide motive means for operating a plurality of container forming machines while such machines are closely positioned one with another.
It will therefore be understood that an object of the present invention is to provide a common drive means for operating a plurality of juxtaposed container forming machines.
Another object of the present invention is to provide improved actuation means for controlling the operation of a stripper punch disposed within the reciprocating ram of a container forming machine.
Still another object of the invention is to provide a compact mechanism in a container forming machine for operating a redraw die in concert with an ironing ram.
Another object of the present invention is to provide a container forming machine with a carriage and ram assembly which is less susceptible to transverse displacement than any known in the prior art.